1. Field of the Invention
The present invention relates to a device and a method for controlling an internal combustion engine including a port injector injecting a fuel into an intake port and an in-cylinder injector directly injecting a fuel into a combustion chamber.
2. Description of the Background Art
An internal combustion engine including a port injector injecting a fuel into an intake port and an in-cylinder injector directly injecting a fuel into a combustion chamber has conventionally been known (see, for example, Japanese Patent Laying-Open No. 63-255539). In the internal combustion engine, fuel injection is switched between the in-cylinder injector and the port injector, depending on a load. In addition, when switching from the in-cylinder injector to the port injector should be made at the time of acceleration of the internal combustion engine, switching between the injectors is delayed, in order to suppress leaner air-fuel ratio or increase in NOx due to switching between the injectors at the time of acceleration.
When switching between the port injector and the in-cylinder injector is made or a fuel injection ratio between the port injector and the in-cylinder injector is considerably fluctuated, a combustion state in the combustion chamber of the internal combustion engine is also significantly varied. Accordingly, even if switching from the in-cylinder injector to the port injector is delayed as in the conventional internal combustion engine described above, satisfactory suppression of torque fluctuation of the internal combustion engine or deviation from a target air-fuel ratio in a transition state such as acceleration has been difficult to achieve.